MATLAB: Speed comparison of two functions using tic/toc

time

Hi, I am supposed to write a function and then to compare my code with built-in MATLAB-function (A\b), how can I do it? I know I can use tic toc function like this:

 function [ z ] = My_Function(A,b)
   tic
   my code 
   toc
%Comparison with built-in
   tic
   MATLABfunction(A,b)
   toc
 end

But is there any function i could use to do deeper comparison and print the results? I would like the output of my function to look like this:

 My_Function(A,b)
 ans = 
 ...
 Time elapsed using your function is: XY seconds, time elapsed using built-in MATLAB function is YX seconds.

Thank you very much in advance

Best Answer

What "deeper" comparison do you think is possible? You already know about the existence of tic and toc, although in many cases, timeit will be a better choice. But if you have some custom block of code, then timeit will not work, unless you encapsulate the entire block of code in its own function.

My point is, if you want some deeper analysis, then you need to explain what "deeper" means to you.

Regardless, it appears that all you need to learn how to do is save the results of the call to toc as a variable, and then display a line of text, converting the number of seconds used into a character string.

So read the help for toc, disp, and num2str.

help toc
help disp
help num2str

If tmycode is the time required for your own code, and tbuiltin is the time for the built-in code to run, then just use disp. Something vaguely like this:

disp(['Time elapsed using your function is:', ...
      num2str(tmycode),' seconds',...
      'time elapsed using built-in MATLAB function is ',...
      num2str(tbuiltin),' seconds.'])

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       averages = [0,0,0,0]; % Holds averages for each calculation
       n = 1000000; 
       vec1 = ones(1,n); 
       for i = 1:numberOfRuns
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           tic 
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           averages(1) = averages(1) + toc; 
           % Matlab function sum
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       disp('Vectorized sum:')
       disp(['  ' num2str(averages(1)) ' seconds average'])
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       disp(['  ' num2str(averages(2)) ' seconds average'])
       disp('Vectorized mean:')
       disp(['  ' num2str(averages(3)) ' seconds average'])
       disp('Matlab function mean:')
       disp(['  ' num2str(averages(4)) ' seconds average'])

When I executed this, I receive the following output:

 Vectorized sum:
   0.00064485 seconds average
 Matlab function sum:
   0.00040692 seconds average
 Vectorized mean:
   0.00040477 seconds average
 Matlab function mean:
   0.00042016 seconds average

It appears that the built-in "mean" function may take slightly longer to execute than "sum", but it is not as dramatic an increase as was seen by timing each function once.

Best Answer

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